Torque converters include a front cover coupled to an engine-side member and a torque converter body fixed at an impeller shell thereof to the front cover. For example, a drive plate fixed to a crankshaft of an engine is fixed to the front cover. In other words, power from the engine is inputted to the front cover. Hence, the front cover is provided with, for instance, a coupling portion for extracting power for driving an oil pump.
Japan Utility Model Application Publication No. S64-36754 describes a torque converter including such a front cover as described above. The front cover described in Japan Utility Model Application Publication No. S64-36754 includes a spline hole in the center part thereof, and a spline shaft for driving a pump is coupled to the spline hole.
In an example shown in FIG. 1 of Japan Utility Model Application Publication No. S64-36754, the front cover is provided with the spline hole in the center part thereof, and a front boss having a bag shape is welded to the engine-side lateral surface of the front cover so as to close the spline hole. However, in the configuration herein described, welding is required and there is a large number of processing steps.
Additionally, in an example shown in FIG. 5 of Japan Utility Model Application Publication No. S64-36754, the front boss is integrated with the front cover by stamping. However, in the configuration herein described, forming the spline hole is quite difficult, and a spline-coupled portion cannot be formed with high strength and high accuracy.